The present invention relates to a method and an apparatus for cleaning articles used in the production of semiconductors, and in particular to a method and an apparatus for cleaning semiconductor wafers, containers for transporting semiconductor wafers (Known as FOUPs), LCD substrates and photomasks.
In the semiconductor industry, various types of articles which are used in the production process need to be cleaned. These articles include auxiliaries, such as photomasks or containers for accommodating semiconductor products, but also semiconductor products themselves, such as wafers and LCD substrates. Therefore, when reference is made in the present application to “articles” that are to be cleaned, this is to be understood as meaning any of these articles.
Since these articles are typically cleaned by means of a liquid, they need to be dried at the end of the cleaning process. It is of great importance that the articles are completely cleaned during the cleaning step and that they are not contaminated again with foreign particles during the drying step. For the drying step, various procedures are known.
According to U.S. Pat. No. 5,562,113, drying of the articles is achieved by means of a stream of hot air. For this purpose, ambient air is sucked in, heated up, filtered and directed into the treatment chamber. This procedure has the disadvantage that, as a result of the external heating of the drying air, only a limited efficiency can be achieved. Furthermore, the supply of outside air always bears the risk that foreign particles are introduced into the treatment chamber although the air is filtered. This is because a compromise has to be made between the effectiveness of the filter on the one hand and the amount of air that can be passed through on the other hand.
In the case of other known apparatuses, which have been sold by the assignee under the type names 300 and 310, outside air is directed into the treatment chamber via a filter without heating-up. Instead, there are arranged infrared radiators inside the treatment chamber. Again, however, outside air is directed into the treatment chamber so that here too the problems mentioned above arise.
EP 0 454 873 A1 discloses a method for drying electronic components in which the components are cleaned in a chamber by means of water vapor. The water vapor condenses on a condenser and flows away as condensate via a line. Only subsequently the components are dried, namely by means of a drying gas, which is supplied from the outside. This method consequently has the same disadvantages as mentioned above, because here too foreign particles are unavoidably carried in by the drying gas.
DE 42 08 665 A1 discloses a method for drying machine parts which are contaminated with processing residues containing oil or grease. The machine parts are cleaned in a cleaning chamber by spraying with a cleaning liquid. For drying the machine parts, air is blown into the cleaning chamber and recirculated by a system of pipes to a blower. In the line between the blower and the cleaning chamber there is a steam/air heat exchanger. When cleaning machine parts, it does not cause any problems if there are foreign particles in the drying air supplied from the outside. For the purposes of the present invention, however, this is unacceptable for the reasons already mentioned above. In addition, an external drying air circuit with a separate condenser has a considerable space requirement.
A further method for cleaning heavy machine parts and an associated apparatus are described in WO 95/29276. In the case of this known method, a cleaning chamber of twice the normal height is provided. When cleaning, a container with machine parts is initially subjected to a cleaning liquid in a lower position in the chamber. After that, the container is raised into an upper position in the chamber and blasted with drying air. Here too, the drying air is circulated in a circuit in which a condenser is arranged. The disadvantages are therefore the same as described above.